1. Field of Invention
This invention relates to a process for the production of pressed bodies from municipal waste or refuse, especially that having a content of wood-based materials, plaster and animal and vegetable substances.
Such refuse which includes household garbage, office and shop litter and certain types of industrial refuse which can be accepted at public garbage dumps, has a certain intrinsic value by virtue of its content of substances in demand. It causes a series of problems and involves expense in that it must be conveyed away and occupies useful space.
2. Description of the Prior Art
Known processes for the treatment of the aforesaid municipal refuse have not been able to make a raw material for further treatment within the current economic framework. It has also been difficult to produce a refuse product suitable for use for most types of further refinement, such as the manufacture of construction sheets or plates and the like.
Swiss patent specification No. 542,292 (Jetzer) describes the production of pressed bodies, especially of fibrous material, in which there is effected an aerobic decomposition of the raw material, primarily for the breakdown of certain organic substances. The assumption has probably been that such substances, especially in food waste, will make it difficult to produce the desired, pressed products or at least will have an unfavourable effect on the quality of those products. The initial composting or aerobic decomposition, moreover, involves a number of disadvantages. There is a demand for equipment and space for carrying out the treatment of the refuse. In addition, such treatment takes time and hence results in direct operational expenses. Furthermore, composting involves the risk of later growth of micro-organisms in the refuse material. This can be counteracted by the addition of preservatives but in quantities exceeding those which would otherwise be necessary.
All these factors make the Jetzer process uneconomic for the treatment of most types of refuse, at least as compared with the alternative costs for the treatment of refuse and production of pressed bodies, for example, construction sheets, which exist to-day.